编辑文本文件中的行

Question

i've tried this code that i found in the internet

File file = new File("file.txt");
        BufferedReader reader = new BufferedReader(new FileReader(file));
        String line = "", oldtext = "";
        while((line = reader.readLine()) != null)
            {
            oldtext += line + "\n";

        }
        reader.close();
        // replace a word in a file
        //String newtext = oldtext.replaceAll("drink", "Love");

        //To replace a line in a file
        String replace = JOptionPane.showInputDialog("Enter what to replace: ");
        String toreplace = JOptionPane.showInputDialog("Enter where to replace: ");
        String newtext = oldtext.replaceAll(replace, toreplace);

        FileWriter writer = new FileWriter("file.txt");
        writer.append(newtext);writer.close();

but mine won't output like this code will do. the output of this code is like this:

unedit:

jojo moyes
kim possible
dexter laboratory

edited: when i enter "mary" to edit "kim"

jojo moyes
mary possible
dexter laboratoty

but mine will be like this

jojo moyes
kim possible
dexter laboratoy
mary possible

mine tho had register before editing. and in the register there is also time that it will store something in the text file. and there goes the edit function if the user wants to edit something in the information that he entered (you get the picture)

EDITED: here's my code

public void Register_Edit_Info() throws IOException{
        FileWriter writeFile=new FileWriter("voters.txt", true);
        BufferedWriter outFile=new BufferedWriter(writeFile);
        File readFile=new File("voters.txt");   
        BufferedReader read=new BufferedReader(new FileReader(readFile));

        String choice2;
        String [] secondMenu = {"Register", "Edit", "Delete", "Back"};

        do{
            choice2=(String)JOptionPane.showInputDialog(null, "Please choose:", "Election 2765", 1, null, secondMenu, secondMenu[0]);
            switch(choice2){
            case "Register":
                String [] menuGender={"Male", "Female"};
                String [] menuStatus={"Single", "Married", "Widow(er)", "Legally separated"};

                do{
                age=Integer.parseInt(JOptionPane.showInputDialog("Age: "));
                while(age<18){
                    JOptionPane.showMessageDialog(null, "Voter should be 18 or above");
                    age=Integer.parseInt(JOptionPane.showInputDialog("Age: "));
                }
                name=JOptionPane.showInputDialog("Full Name: ");
                gender=(String)JOptionPane.showInputDialog(null, "Gender:", "Election 2765", 1, null, menuGender, menuGender[0]);
                if(gender=="Male"){
                    gender="Male";
                }
                else{
                    gender="Female";
                }
                dBirth=JOptionPane.showInputDialog("Date of Birth: ");
                pBirth=JOptionPane.showInputDialog("Place of Birth: ");
                address=JOptionPane.showInputDialog("Address\n(Province, City/Municipality, Barangay, House No./Street: ");
                status=(String)JOptionPane.showInputDialog(null, "Civil Status:", "Election 2765", 1, null, menuStatus, menuStatus[0]);
                if(status=="Single"){
                    status="Single";
                }
                else if(status=="Married"){
                    spouse=JOptionPane.showInputDialog("Spouse Name: ");
                    status="Married(Spouse: "+spouse+")";
                }
                else if(status=="Widow(er)"){
                    status="Widow(er)";
                }
                else{
                    status="Legally Separated";
                }
                citizenship=JOptionPane.showInputDialog("Citizenship:");
                job=JOptionPane.showInputDialog("Profession/Occupation: ");
                tin=JOptionPane.showInputDialog("Tin Number: ");
                father=JOptionPane.showInputDialog("Father's Full Name: ");
                mother=JOptionPane.showInputDialog("Mother's Full Name: ");
                votersNumber++; 

                vNumber=Integer.toString(votersNumber);

                outFile.append(vNumber+"/"+name+"/"+age+"/"+gender+"/"+dBirth+"/"+pBirth+"/"+address+"/"+status+"/"+citizenship+"/"+job+"/"+father+"/"+mother);
                outFile.newLine();

                selectYN=JOptionPane.showInputDialog("You are now registered. Do you want to register more?\n[1]Yes [2]No");
                }while(!"2".equals(selectYN));

                break;
            case "Edit":
                vNumForEdit=JOptionPane.showInputDialog("Enter voters number: ");
                String line=null, oldtext="";

                while((line=read.readLine())!=null){
                    oldtext+=line+"\n";

                    String [] info=line.split("/");
                    if(info[0].matches(vNumForEdit)){
                        String [] forEditMenu={"Name", "Age", "Gender", "Date of Birth", "Place of Birth", "Address", "Civil Status", "Citizenship", "Profession/Occupation", "Father's Name", "Mother's Name"};
                        forEdit=(String)JOptionPane.showInputDialog(null, line+"\n\nPlease select what you want to edit", "National Election 2765", 1, null, forEditMenu, forEditMenu[0]);
                        switch(forEdit){
                        case "Name":
                            oldName=JOptionPane.showInputDialog("Enter old name: ");
                            newName=JOptionPane.showInputDialog("Enter new name: ");

                            String newText = oldtext.replaceAll(oldName, newName);
                            outFile.append(newText);                            
                            break;
                        }
                    }
                }
            case "Delete":
                break;
            }
        }while(choice2!="Back");
        read.close();
        outFile.close();
    }

Answer 1

This Answer is for the first portion of your question.(before edit).

public static void main(String[] args) throws FileNotFoundException,IOException {
        File file = new File("file.txt");
        BufferedReader reader = new BufferedReader(new FileReader(file));
        String line = "", oldtext = "";
        while((line = reader.readLine()) != null)
            {
            oldtext += line + "\n";

        }
        reader.close();
        System.out.println(oldtext);
        // replace a word in a file
        //String newtext = oldtext.replaceAll("drink", "Love");

        //To replace a line in a file
        String replace = JOptionPane.showInputDialog("Enter what to replace: ");
        String toreplace = JOptionPane.showInputDialog("Enter where to replace: ");
        String newtext = oldtext.replaceAll(replace, toreplace);

        System.out.println(newtext);
        java.io.FileWriter writer = new java.io.FileWriter("file1.txt");
        writer.write(newtext);
        writer.close();
    }

When first prompt open I write "kim" and where to replace , I write "marry" and the output like this. I think your code is fine except not to use append() for FileWriter. you should use write() method for FileWriter.

EDIT: Use different file name (I don't know about if reading and writing operation occur for same file.) for FileWriter and for initialization you can use

FileWriter writeFile=new FileWriter("voters1.txt");

And let me know if the problems is solved.